|Year : 2022 | Volume
| Issue : 3 | Page : 266-268
Isha Chaturvedi, Pradeep Sharma
Strabismus Pediatric and Neuro-Ophthalmology Services, Centre for Sight Eye Institute, Safdarjung Enclave, New Delhi, India
|Date of Submission||10-Oct-2022|
|Date of Acceptance||10-Oct-2022|
|Date of Web Publication||02-Nov-2022|
Strabismus Pediatric and Neuro-Ophthalmology Services, Centre for Sight Eye Institute, Safdarjung Enclave, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Chaturvedi I, Sharma P. Accommodating children. Oman J Ophthalmol 2022;15:266-8
We read with interest the article reporting the clinical characteristics and outcome of Omani children with accommodative ET. Esotropias often present as a constant esodeviation occurring in infancy or early childhood with accommodative esotropia (AET) contributing to 53% of all childhood esotropias in the general population. The risk factors for the development of esotropia include anisometropia, hyperopia, neurodevelopmental anomalies, prematurity, low birth weight, craniofacial or chromosomal abnormalities, maternal smoking during pregnancy, and family history of strabismus. As already pointed out by the authors, the prevalence of AET in the western population is 1%–2%, and most cases manifest between 1.5 and 4 years of age.
In general, when compared to exodeviations, esodeviations are poorly controlled due to our limited divergence amplitude (6–8 prism diopters [PD], as against 30 PD for fusional convergence) and tend to be more constant. Poor binocular fusion, impaired stereopsis, and amblyopia are more common with esodeviations. However, it is seen that late-onset acquired or intermittent esotropias usually have good binocular fusion; hence, the age of onset of esotropia is important in determining binocular fusion potential. AETs typically appear early (range 3 months–6 years in the present study) and are usually intermittent at the onset but become constant with time. They are associated with significant hyperopia (+2 D or more) and are concomitant in nature, often hereditary, sometimes precipitated by stress, frequently associated with amblyopia, and occasionally diplopia (especially with older onset). These characteristics make their diagnosis and management unique and different from other types of esotropias.
AETs are generally classified into fully refractive normo-accommodative, hyper-accommodative (with high AC/A ratio), hypo-accommodative, and partially accommodative (with a nonaccommodative component) but can be clinically categorized into fully accommodative esotropia (FAET) which may be: refractive (normal AC/A ratio), nonrefractive (high AC/A ratio), and partially accommodative esotropia (PAET) as has been done in this study. In the present study, about 47% of the total patients had FAET, and 27% presented with a high AC/A ratio. In refractive normo-AET, patients have uncorrected hyperopia and as a result, an increased accommodative effort to focus the retinal image. Accommodation is accompanied by convergence. If the patient's fusional divergence mechanism is insufficient, there are over-convergence and esotropia results. The angle of esotropia in such cases is approximately the same at distance and near fixation and is generally between 20D and 30D. Patients with this type of esotropia have an average of +4.00 D of hyperopia and a normal AC/A (3–5 PD/D) ratio. In high AC/A ratio (hyper-accommodative) esotropia, patients have an excess convergence response for the amount of accommodation required to focus while wearing their full cycloplegic correction. The deviation is present only near or is much larger (>10 PD) at near and corrected by near-add in the form of bifocals. The refractive error in such cases averages +2.25 D. This type of esotropia can be seen in hyperopia, emmetropia, or even myopia. In partial AET, there is a reduction in the angle of esotropia but with a residual deviation (>10 PD) even with hyperopic full correction. This can occur secondary to neglected AET, due to contraction of the conjunctiva, muscles, and Tenon's capsule. It can also result from the decompensation of a pure refractive AET (FAET). Often, surgical treatment is warranted for the residual deviation.
In the present study, the age of onset of esotropia in the PAET group was significantly younger, with a longer time delay in reporting. As pointed out earlier, delayed initiation or partial compliance with an optical correction may lead to PAET. Earlier onset (≤2 years of age) of the deviation seen in such patients may be the reason for reduced stereo acuity in this group. Furthermore, FAET patients can achieve orthophoria with full correction, thereby maintaining good binocularity. The mean hyperopia overall was about 4 D with more than one-third of the patient having amblyopia. Anisometropia and amblyopia were more common in PAET than FAET. The mean angle of deviation for near at presentation was similar in both groups. For distance, the deviation was more in the PAET group.
Before discussing the management of AETs, it is important to be familiar with the normal process of emmetropization. Human infants are hyperopic at birth with a mean refractive error of 1–1.25 D during the 1st year of life. About 5% of infants have >3D of hyperopia between 6 and 9 months of age. It has been observed that if hyperopia at 1 year of age is more than 2.50 D, it is likely to continue to increase in approximately half of these patients. Often increasing hyperopia has been documented before the onset of esotropia. Normal children become less hyperopic or more myopic after 7–8 years of age as a part of the emmetropization process. However, this hyperopia changes slowly in esotropes given their full glasses correction. In the present study, patients with FAET had higher hyperopia than those with PAET and an increase of 0.5 D in hyperopia was noted over 5 years. Raab documented a decrease in hyperopia at the rate of 0.18 D per year in esotropic children when compared to 0.22 D per year in normal hyperopic children. Hence, hyperopic esotropes behave differently and there is conflicting evidence that full correction of hyperopia may impede normal emmetropization. Hence, the goal of management of AET should include (1) providing full cycloplegic correction, (2) management of amblyopia if any, and (3) gradual weaning of spectacles.
Contrary to the older practice of under-correction of hyperopia in AET to allow normal emmetropization, the trend has shifted to prescribing full cycloplegic correction. This is the first step in the treatment. In most FAET patients, the eyes are aligned within 10 PD for distance and near with good binocularity. A subset of these patients may have residual esotropia near which may need near-add bifocal spectacles. Such children have defective near-fusion and adding near-add helps relax their accommodation, thus reducing convergence. Bifocals with a flat-top segment that bisects the pupil are desirable to ensure that the child does not peer over the bifocal add. Older children can be trained to use progressive add spectacles too. It has been observed that there is a decrease in the near deviation with time, with the development of fusion, and stereopsis for both distance and near. Bifocal power can be gradually weaned in 0.50–1.00 D steps, starting at about 7 years of age, with complete riddance of bifocals by the age of 10–12 years. If weaning from bifocals is not possible, surgery may be considered. If, after wearing full hyperopic correction, a residual esotropia (>10 PD) for distance and near exists, it is a partly AET and the nonaccommodative part needs to be addressed surgically. Such patients cannot fuse and bifocals cannot correct the esotropia for distance. The procedure of choice is medial rectus recession. Alternatively, prism adaptation may be tried. Before planning surgery, it is important to understand that it is only to align the eyes, and spectacle wear must be continued postoperatively. In older patients, refractive surgery may be considered to reduce the hyperopic error and improve ocular alignment. PAET is often associated with amblyopia and it is advisable to treat the amblyopia first so that fusion is established before surgery. At times, the resolution of the nonaccommodative part of the treatment may even obviate the need for surgery.
Full-time wear must be emphasized to the parents because intermittent removal of the spectacles will not relax accommodation and esotropia may reappear on such occasions. Most children achieve orthophoria within 4–8 weeks of full-time spectacle wear. Amblyopia may respond to spectacle correction alone; if this is not the case, amblyopia therapy should be instituted. In the presence of good binocular fusion and the natural decrease of hyperopia, one can gradually reduce the hyperopic correction to create a small esophoria, which stimulates fusional divergence. However, good compliance with spectacles and amblyopia therapy is a prerequisite for weaning off glasses. In the present study, compliance with glasses was reported as good in more than 90% of subjects, and the overall reduction in amblyopia was 40% to 6% over a 5-year follow-up.
The study also describes that 75% had binocularity with Bagolini glasses but measurable stereopsis was seen in lesser numbers, more so in the FAET group. About 50% of PAET had impaired binocularity, implying that the full correction of the esotropia was not there or at least not early enough. This highlights the role of early detection and periodic assessment to ensure full correction of esotropia.
Moreover, while this study is of only 5 years' duration and could not document any decrease, a longer study would also show the decrease in hyperopia over the subsequent decades: 8% in 5 years, 20% in 10 years, and 37% by 20 years of age as reported by Mohney.
To conclude, the present study, in accordance with previous studies highlights the more favorable outcome of FAET compared to PAET in terms of fusion, stereopsis, and need for surgery. Delays in treatment, younger age at presentation, and anisometropia are associated with adverse outcomes. Prescribing the full cycloplegic hyperopic correction should be the norm and gradual weaning of spectacles attempted while ensuring that adequate fusion is maintained for distance and near. Many of these patients continue to be hyperopic well into adulthood. Compliance with therapy and education of the parents about the importance of full-time spectacle wear, amblyopia therapy, and the need to continue wearing spectacles even postsurgery is of utmost importance.
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